Braided structures are configured in two main ways, tubular braids and flat braids. A conventional tubular braided structure can be accomplished using standard braiding technology that has been in existence for several centuries. The standard tubular braided structure can be braided over material (a core) or left as a hollow tube. As braiding is a highly efficient process and can be operated in clean environments, many medical devices are manufactured using this process such as stents, sutures and catheters.
A typical machine for producing a tubular braid is shown in U.S. Pat. No. 7,237,466, incorporated by reference herein in its entirety, in which FIG. 1 shows a plate 12 having a track comprising two intersecting paths, along which a plurality of carriers 15 are advanced by eight rotating horngears (transfer plates 14). Carriers 15 travel along one of the paths in a clockwise-direction, and carriers travel along the other path in the counter-clockwise direction to form the tubular braid.
Flat braids are created on braiding equipment similar to that used for tubular braids. These braided constructions are typically use in electronics for ground wiring and other high current environments. Sometimes a tubular braid is overbraided onto a flat braid as an insulator. Machines arranged for flat braiding differ from machines arranged for tubular braiding in that flat braiding arrangements cause the yarn carriers to reverse direction at the edge of the braid, instead of continuing in closed curved paths.
Over the years, variations of braiding machines have been developed to produce either a tubular braid or a flat braid, or to switch between the tubular braiding mode and flat braiding mode during operation.
U.S. Pat. No. 2,148,164 to Krippendorf, incorporated by reference herein in its entirety, describes a machine that switches between tubular and flat braiding modes, with a pair of special horngears that pass bobbin carriers back and forth in the tubular braiding mode, or reverse the direction of the bobbin carriers in the flat braiding mode. A retarding mechanism is needed to provide phase and rate matching when the operating mode is switched.
U.S. Pat. No. 6,907,810 to Kim, incorporated by reference herein in its entirety, describes a system that is operable to produce a single tubular braid, or a pair of rectangular braids. It is thus possible to produce a braid having an eye where the single braid bifurcates into two rectangular braids.
Improved methods and apparatus are desired.